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PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 77 insertions, 0 deletions

diff --git a/pkg/sentry/fs/save.go b/pkg/sentry/fs/save.go
new file mode 100644
index 000000000..bf2a85143
--- /dev/null
+++ b/pkg/sentry/fs/save.go
@@ -0,0 +1,77 @@
+// Copyright 2018 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package fs
+
+import (
+	"fmt"
+	"syscall"
+
+	"gvisor.googlesource.com/gvisor/pkg/log"
+)
+
+// SaveInodeMappings saves a mapping of path -> inode ID for every
+// user-reachable Dirent.
+//
+// The entire kernel must be frozen to call this, and filesystem state must not
+// change between SaveInodeMappings and state.Save, otherwise the saved state
+// of any MountSource may be incoherent.
+func SaveInodeMappings() {
+	mountsSeen := make(map[*MountSource]struct{})
+	for dirent := range allDirents.dirents {
+		if _, ok := mountsSeen[dirent.Inode.MountSource]; !ok {
+			dirent.Inode.MountSource.ResetInodeMappings()
+			mountsSeen[dirent.Inode.MountSource] = struct{}{}
+		}
+	}
+
+	for dirent := range allDirents.dirents {
+		if dirent.Inode != nil {
+			// We cannot trust the root provided in the mount due
+			// to the overlay. We can trust the overlay to delegate
+			// SaveInodeMappings to the right underlying
+			// filesystems, though.
+			root := dirent
+			for !root.mounted && root.parent != nil {
+				root = root.parent
+			}
+
+			// Add the mapping.
+			n, reachable := dirent.FullName(root)
+			if !reachable {
+				// Something has gone seriously wrong if we can't reach our root.
+				panic(fmt.Sprintf("Unreachable root on dirent file %s", n))
+			}
+			dirent.Inode.MountSource.SaveInodeMapping(dirent.Inode, n)
+		}
+	}
+}
+
+// SaveFileFsyncError converts an fs.File.Fsync error to an error that
+// indicates that the fs.File was not synced sufficiently to be saved.
+func SaveFileFsyncError(err error) error {
+	switch err {
+	case nil:
+		// We succeeded, everything is great.
+		return nil
+	case syscall.EBADF, syscall.EINVAL, syscall.EROFS, syscall.ENOSYS, syscall.EPERM:
+		// These errors mean that the underlying node might not be syncable,
+		// which we expect to be reported as such even from the gofer.
+		log.Infof("failed to sync during save: %v", err)
+		return nil
+	default:
+		// We failed in some way that indicates potential data loss.
+		return fmt.Errorf("failed to sync: %v, data loss may occur", err)
+	}
+}